This invention relates to novel blue mica flake pigments.
Colored pigments and more particularly colored lustrous pigments are of increasing interest in a great variety of fields, for example, in cosmetics and as additives to synthetic resins, varnishes and paints.
A number of mica flake lustrous pigments and naceous pigments are known. The colors of these pigments are normally produced by interference, but they can also be based partially on colored metallic oxide additives. The thus-attainable play of colors is, however, limited. Pigments having blue or blue-tinged color tones in a satisfactory nuancing have not been attainable heretofore.
Processes are known (see German Patent No. 1,192,353 and the corresponding U.S. Pat. No. 2,995,459), according to which lustrous pigments can be directly dyed by the precipitation thereon of colored precipitates. However, these conventional processes are unsuitable for a precipitation of Berlin blue, because the latter forms colloidal deposits during direct precipitation, which settle only partially or not at all on the flakes of the pigment to be dyed. This leads to irreproducible batches, to considerable difficulties during filtering, and, in particular, no nacreous luster effect can be obtained in this way. However, by adhering to the conditions of the process of this invention, colored pigments are obtained having a high gloss and a strong chroma.
In accordance with this invention, mica flake pigments with blue color tones are obtained. These pigments have a very high color strength [chroma], and can be produced in a palette of staggered color nuances of blue tones or blue-tinged colors. Such color tones have heretofore been unaccessible. Such pigments are of special interest in the cosmetic field, because the dye employed in this invention is permitted for this application.